Juanjuan Shi will be presenting her PhD work on Tuesday May 26th at 10:00am in CB B012. She will give a talk on “Morphology-based feature extraction method and resampling-free fault identification technique for bearing condition monitoring”. Her supervisors are Dr. Ming Liang and Dr. Dan-Sorin Necsulescu. Abstract of the talk is below.

Date: May 26th, 2015

Time: 10:00am

Location: CBY B012

Abstract

The effectiveness of vibration-based bearing fault diagnosis is often handicapped by 1) background noise and compounded effects of interferences for constant speed case, and 2) non-stationarity plus the two aforementioned factors for time-varying speed case. To address these issues and overcome the shortcomings of filter-parameter-dependence and error-propagation of conventional methods, novel methods are proposed in this work.
Two morphology-based methods are first proposed to extract fault features without prefiltering for constant speed case. The first method, based on fractal dimension (FD), can suppress interferences and highlight fault-induced impulse envelope by mapping the signal into FD representation. Its effectiveness, however, deteriorates with the interference frequency increase. Hence, the second method, which isolates impulses from interferences and noise via resonance behaviors, is developed. Both methods are independent of frequency information and can reveal fault features without prefiltering.

For bearings under variable speed, since resampling propagates error and complicates the process substantially resampling-free methods are innovatively proposed. A resampling-free order spectrum is derived via the joint application of generalized demodulation and short time Fourier transform, from which not only the existence of faults but also the location of faults can be revealed. Nevertheless, the success of this method relies upon an effective envelope demodulation. Based on the proposed resampling-free order spectrum, a time-frequency analysis technique termed dual demodulation transform is devised and applied to bearing fault identification, without envelope procedure.

And coming up next on the 19th May at 10:00am is Charles Blouin. Again, we’ll be in CBY B012 and I’ve been told there will be master coffee making and expert cookie tasting to go along with the seminar.

Charles will be talking about “Trajectory Optimization for a Small Airship Using an Optimal Control Solver”.

Airships demonstrate long endurance and long range capabilities. Those characteristics make them ideal for telecommunication, surveillance and long endurance missions. To maximize flight time or reduce the time required to attain an objective, optimal trajectories are computed before a dirigible performs a maneuver. This seminar will demonstrate how the optimal trajectory problem can be formulated as a general optimization problem, and how it can be solved with a pseudo-spectral optimal control solver. Experimental and simulation results will be presented and discussed. In general, optimal control solvers can be used to optimize dynamical systems with respect to a performance index and subject to time varying inputs.

OMEGA is offering tea, coffee and cookies. We’ll be in CBY B012 at 10:00am. The abstract of Armel’s talk is below.

Abstract

The core of the CANadian Deuterium Uranium (CANDU) nuclear reactor consists of several pressure tubes containing bundles of fuel elements (“rods”) stacked end to end. The fuel rods are cooled by liquid coolant (heavy water) flowing axially in the interconnected subchannels formed by the rods. The thermal-hydraulic performance of the reactor, and particularly the surface temperature of the rods and the temperature of the coolant depend strongly on the turbulent flow structure in the subchannels.

Typically, the Reynolds number of a CANDU reactor running at full power is about half a million. During start-up or shut down, the Reynolds number drops to a much lower value and tends to fluctuate. Although a large number of experimental and computational studies have examined flows in rod bundles, the effect of Reynolds number on the structure of turbulence and the development of vortex networks have not been documented sufficiently.

This experiment aims at investigating experimentally the structure of turbulent flow in the subchannels of a large scale, 60o section of a CANDU 37-rod bundle at Reynolds numbers equal to 50,000, 100,000 and 130,000. The mean flow distribution, the turbulent kinetic energy, the Reynolds stresses, coherent structure characteristics and other turbulence indicators were measured using constant temperature hot-wire anemometry. It was demonstrated that coherent structures, whose generation is attributed to the gap instability mechanism and which form a vortex network, originated very close to the rod bundle inlet. The convection speed of the vortex network increased with bulk velocity, whereas the spacing between the coherent vortices remained unaffected.

To kick off the first seminar of our summer seminar series, Saeed Rahbarimanesh presented his talk on the direct numerical simulation of mixing layers. Supervisor Dr. Catherine Mavriplis was in attendance along with a small but alert crowd. Something about coffee and cookies keeps people alert in the morning…

I was sick the day that Tochukwu Ezeanochie (aka TC) gave his seminar so I missed the usual photo op. But I dug something up from my files. So…better late than never, here’s the photo of TC with one half of the supervisory team, Dr. Fabio Variola.